The DDG-51's throttle is named the programmed control lever (PCL). It has two scales to indicate throttle position: first, the traditional 1/3d, 2/3d, standard, full, and flank markings for ahead bells, and 1/3d, 2/3d, and full for backing bells; second, it is annotated by a 0-10 scale (in 0.1 increments), with 0 at stop and 10.0 indicating the maximum flank bell.
Note that a DDG-51 engineering system schedules pitch and revolutions per minute (RPM) differently from a destroyer or guided-missile cruiser. At zero knots, the shafts are rolling at about 60 RPM and 7% pitch. To increase speed, the machinery control system begins increasing pitch, but it does nothing (or very little) to change the amount of fuel going to the engines. Thus, as pitch is added, shaft speed slows until you hit about 6-7 knots, when pitch is at 100% and the shaft RPM has slowed to about 34. To increase speed further, the system now increases the fuel to the engines to increase RPM.
The PCL has two modes of operation. The most commonly used mode is pitch and RPM. In this mode, the conning officer orders a particular speed and the lee helmsman consults a chart to convert that speed to a PCL setting for that engineering configuration. For example, the conning officer may order, "All ahead 2/3d for 9 knots." The lee helmsman looks up 9 knots in the PCL table, converts that to a PCL setting of 3.1, and sets the PCL accordingly. The other mode of operation is called maneuvering bells. This mode—intended for pier work—detracts from the ability to precisely pick your speed. But it offers quicker reaction time because the lee helmsman need only get the PCL in the ballpark of the ordered bell and the computer will automatically select the predetermined pitch and RPM setting for that bell.
Probably because of the inflexibility of the maneuvering combinations mode, a third mode has evolved, which is a mix of the two. The PCL is left in its default pitch and RPM mode, but the lee helmsman uses predefined marks on the throttles when answering a bell in a maneuvering situation. For example, when the conning officer orders "All ahead 1/3d," the lee helmsman can set the PCL at a predetermined 1/3d setting without consulting the table. The predetermined setting is marked on the PCL by a small dot. This offers the quick reaction of true maneuvering combinations while maintaining the flexibility of the pitch and RPM mode.
The solution offered here leverages off this feature and simply changes the marks of the back 1/3d and back 2/3d bells. I recommend conning officers experiment to find the exact settings for their ships—but the settings here will get you close. The original back 1/3d setting was at -1.0; the new setting is -0.8. The original back 2/3d was -2.0; the new setting is -1.5.
Commander Mosher is commanding officer of the USS Mahan (DDG-72).